Low odor solvents



Aug. 9, 1960 l. A. ELDIB E'I'AL LOW ODOR SOLVENTS Filed March 6. 1958 moEmEwm momDm 1 ommu Laurence F. King inventors lbruhim A. Eldib B WM Attorney United States L'OW onon SOLVENTS Filed Mar. 6, 1958, Ser. No. 719,690

14 Claims. (Cl. 208-218) The present invention relates to hydrocarbon solvents boiling in the range between about 100 and about 500 P. which have low odor intensities and high solvent powers and to methods for the production of such solvents from petroleum hydrocarbons.

Hydrocarbon solvents boiling between about 100 F. and about 500 F. are widely used in the paint and varnish and dry cleaning industries, in the manufacture of printing inks, insecticides and furniture polishes, and many other applications where the odors generally associated with such solvents are quite undesirable. It is known that the offensive odors of such hydrocarbon solvents are due primarily to the presence of sulfur compounds, aromatics, and, to a lesser extent, naphthenic compounds. The trend in solvent manufacture in recent years has therefore been to employ highly refined petroleum distillates substantially free of sulfur as solvent base stocks and to materially reduce the concentration of aromatics and naphthenes in such base stocks by solvent extraction or similar treatment. It has been found that solvents of this type have reasonably good odor characteristics and in this respect are superior to solvents consisting of straight run petroleum distillates. Ditficulties have been encountered, however, in providing such solvent with the necessary solvent powers. Aromatic hydrocarbons have high Kauri-Butanol values and are thus excellent solvents. The Kauri-Butanol values of naphthenes are lower than those of aromatics and those of parafiins are very low. The complete elimination of aromatics and naphthenes from solvents in order to improve their odor thus results in a substantial sacrifice in solvent power and it is necessary to include appreciable quantities of these materials in most solvents even though they have an adverse effect upon solvent odor.

The present invention provides a new class of hydrocarbon solvents boiling in the range between about 100 and about 500 F. which contain constituents having relatively high solvent powers and relatively inoffensive odors. The invention is based upon the discovery that aromatic hydrocarbons boiling in the narrow range between about 360" F. and about 390 F., predominantly ethyl and propyl di-substituted benzenes and tetramethyl benzenes, have odors which are much milder than odors of aromatics boiling above and below that range. By adding aromatics boiling within this comparatively narrow range to desulfurized petroleum hydrocarbons boiling between about 100 and about 500 F. which are substantially free of aromatics, it is possible to produce solvents which for a given odor level have appreciably higher solvent powers than conventional solvents. For a given solvent power, the solvents of the invention have odors which are much less offensive than those of conventional solvents. The solvents of the invention are suitable for use in a wide variety of applications wherein relatively low odor solvents having high solvent power are required.

I The solvents of the invention may be produced in a number of diiferent ways, depending upon the characteristics of the feed stocks employed and the odor level and solvent powers desired. It is generally preferred, however, to substantially eliminate aromatic hydrocarbons from a desulfurized distillate petroleum fraction boiling between about and about 500 F. by solvent extraction, hydrogenation, selective adsorption or the like and then add aromatics boiling between about 360 and about 390 F. in order to increase the solvent power of the substantially nonaromatic distillate. The solvents of the invention may also be produced by blending the low odor aromatics into a parafiinic stream derived from alkylation, olefin polymerization or the like.

In a particularly preferred embodiment of the inven-. tion. a distillate petroleum fraction boiling in the range between about 100 F. and about 500 F. is first desulfurized by hydrotreating and thereafter hydrogenated in the presence of a nickel-on-Kieselguhr or similar nickel-containing hydrogenation catalyst in order to prepare a substantially nonaromatic solvent base stock. The preliminary hydrotreating step prevents poisoning of the catalyst in the subsequent hydrogenation step in addition to correcting odor deficiencies due to the presence of sulfur compounds. The hydrotreating reaction may be carried out at temperatures in the range of from about 400 to about 800 F., preferably about 600 to 700 F. Presures may vary from about 100 to about 1000 p.s.i.g. and preferably range between about 250 to about 500 p.s.i.g. Hydrogen-to-feed ratios of from about 100 to about 2000 standard cubic feet per barrel, preferably about 400 to 600 standard cubic feet per barrel, may be used. Suitable hydrotreating catalysts for purposes of the invention include cobalt molybdate, molybdenum sulfide, molybdenum oxide, molybdena on alumina and similar molybdenum-containing catalysts. Hydrotreating space velocities may range from about 1 to about 5 volumes per volume per hour. Under these conditions, sulfur compounds in the distillate are readily converted to hydrogen sulfide which can subsequently be removed and, in addition, unsaturates, nitrogen and oxygen compounds and other un-. stable constituents are converted to more stable materials. Because of these beneficial effects, it is generally prefered to hydrotreat the distillates to be used in solvent manufacture, even though solvent extraction, adsorption or a similar process is to be used for subse quent removal of aromatics in place of the preferred hydrogenation step. Other desulfurization processes such as hypochlorite sweetening, caustic sweetening and the like may also be used however.

The conditions employed for hydrogenating the desulfurized distillate in order to convert aromatics to naphthenic compounds are somewhat more severe than those employed in the hydrotreating step. The hydrogenation may be carried out at temperatures of from about 350 to about 600 F., preferably about 400 to 450 F. Pressures of from about 300 to 1500 p.s.i., preferably about 750 to about 850 p.s.i., may be used. Hydrogen rates may be varied from about 500 to about 5000, preferably from about 1500 to about 3000, standard cubic feet of hydrogen per barrel of feed. The preferred hydrogenation catalysts is nickel-on-Kieselguhr, although other nickel catalysts used heretofore for hydrogenation purposes may also be employed. Space velocities during hydrogenation may range from about 1 to about 30 volumes per volume per hour or higher. Such hydrogenation results in the conversion of aromatics to naphthenes and permits the recovery of hydrogenated distillates containing aromatics in concentrations of about 2% or less. i

The substantially nouaromatic fraction used as the solvent base stock may also be prepared by extraction using a solvent selective for aromatics. Selective s01- vents in which aromatics are preferentially soluble include phenol, cresol, nitrobenzene, nitrophenol, chlorin ated phenol, furfural, aniline, pyridine, liquefied sulfur dioxide, aqueous diethylene glycol, ammonia and the like. These may be used with or without additional modifying solvents. Solvent extraction processes employing these solvents are normally carried out in countercurrent contacting towers but may be conducted batchwise if desired. Temperature and pressure conditions employed in such extraction processes may vary widely depending upon the characteristics of the particular solvents employed. Extraction with phenol, for example, may be carried out at a temperature range from about 100 F. to about 250 F., while with sulfur dioxide it is necessary to use temperatures in the range of from about 30 F. to about F. Pressure conditions vary similarly. Such solvent extraction processes are well known to those skilled in the art and need not be described at length for purposes of the present invention.

The 360390 F. aromatics fraction which is blended with the desulfurized low-aromatics or nonaromatic distillate in order to increase its solvent power in accordance with the invention may be segregated from an extract phase obtained by the solvent extraction of a low boiling petroleum distillate, from the product stream from a selective adsorption process or from a number of other sources. The distillate from which the aromatics are segregated may be desulfurized prior to the segregation step or the aromatics fraction may later be desulfurized before it is blended into the substantially nonaromatics fraction. It is preferred, however, to employ for this purpose a 360-390 F. cut from a desulfurized petroleum distillate containing both aromatics and nonaromatic compounds. The presence of the nonaromatic compounds does not seriously affect the odor of the finished solvents. It is, however, necessary to employ slightly greater quantities of such a cut than it would be if a pure aromatic out were used.

The amount of the 360-390" F. aromatics-containing fraction which is blended with the low aromatics or substantially nonaromatic distillate in order to produce the solvents of the inveniton may vary widely depending upon the odor intensity and solvent powers desired. While from about 1% to about 25% aromatics may generally be blended with the low aromatics or nonaromatic fraction, it is particularly preferred to limit the aromatics content to from about 4 to about 8%. It has been found that solvents of especially low odor intensity can be prepared in this manner. The presence of the aromatics in concentrations of from about 4 to 8% appears to have a masking efiect upon the odor of naphthenes in the solvent. It has been found that aromatics contents below about 4% and above about 8% give stronger odors than solvents containing aromatics within this range possess. The exact aromatics concentration necessary to produce optimum odor characteristics will vary within the 4 to 8% range depending upon the concentration of naphthenes in the solvent.

The exact nature and objects of the present invention may be more fully understood from the following description of a preferred process for producing improved solvents of low odor intensity and high solvent powers and from the accompanying drawing illustrating that process.

Referring now to the drawing, a petroleum distillate boiling in the range between about 100 F. and about 500 F., between about 300 and 400 F. for example, is introduced through line 1 into furnace 2 where it is heated to a temperature in the range of from about 400 to about 700 F. The heated feed passes through line 3 and is mixed with hydrogen introduced at a pressure of from about to about 1000 p.s.i.g. through line 4. The hydrogen and feed pass through line 5 into hydrotreating zone 6 in which cobalt molybdate or a similar hydrotreating catalyst is disposed. Although only one hydrotreating zone is shown in the drawing, it will be understood that a plurality of zones may be employed in order to permit periodic regeneration of the catalyst. The hydrogen feed rate may vary from about 100 to about 3000 standard cubic feet per barrel of feed and the space velocity may range from about 1 to about 5 volumes per volume per hour. Light hydrocarbon gases containing substantial quantities of gaseous hydrogen may be used in lieu of pure hydrogen if desired. Under these conditions sulfur compounds in the feed are hydrogenated and hydrogen sulfide is liberated, unsaturated compounds are saturated, and nitrogen and oxygen compounds are converted to more stable materials.

The hydrotreated product is withdrawn from the hydrotreating zone through line 7 and condensed in condenser 8. The liquid product is then passed through line 9 into liquid-vapor separator 10 where hydrogen and hydrogen sulfide are removed. The gaseous products pass overhead through line 11. A portion of the gas stream may be purged through line 12 and the remainder is recycled through line 13 and blended with the incoming feed materials. The hydrotreated liquid product is passed through line 14 into distillation zone 15 and distilled. The distillation may be carried out in the presence of ammonia or a similar inert gas to reduce autooxidation responsible for odor degradation. The overhead product from distillation zone 15, removed through. line 16, consists essentially of residual hydrogen sulfide and light gases. A liquid product boiling below about 360 F. is removed through line 17. A second product boiling between about 360 and 390 F. is taken off through line 18 and a bottoms product boiling above about 390 F. is removed through line 19.

The liquid product drawn through line 17 and the bottoms product taken off through line 19 are combined and passed through line 20 into furnace 21 where they are heated to the hydrogenation temperature of about 350 to about 600 F. The intermediate product from distillation zone 16 is passed through line 18 into storage zone 22, where it may be stored under a blanket of ammonia or other inert gas to reduce autooxidation. The heated distillate is withdrawn from furnace 21 and passed through line 23 where it is mixed with hydrogen introduced through line 24 prior to its introduction into bydrogenation zone 25. Again, the hydrogen employed need not be pure hydrogen. Light hydrocarbon gas streams containing appreciable quantities of gaseous hydrogen may be used and are often preferred. In addition to hydrogen such streams may contain methane, ethane, propane, butane and the like. The hydrogenation conditions in zone 25, wherein nickel or a similar hydrogenation catalyst is disposed, include temperatures of from about 350 to about 600 F., pressures of from 300 to 1500 p.s.i.g. and hydrogen-to-feed ratios of from about 500 to about 6000 standard cubic feet per barrel. The hydrogenated product is withdrawn from zone 25 through line 26 and condensed in condenser 27. The condensed liquids are then passed into liquid vapor separator 28 where gases are taken overhead through line 29 and recycled to the hydrogenation zone through line 30. A portion of the gas stream may be purged through line 31 in order to maintain impurities at an acceptable level.

The hydrogenated product recovered from the separation zone 28 passes through line 32 into caustic washing zone 33. Caustic is introduced through line 34 and passes countercurrent to the hydrocarbons, removing polymeric materials and other impurities therefrom. Spent caustic is withdrawn from line 35. The caustic washed hydrocarbon stream is taken overhead from the washing zone through line 36 and passed through scrub her 37 where it is water washed. Water may be introduced through line 38 and withdrawn through line 39. The washed product is then passed through line 40 into storage zone 41. The product may be stored under a blanket of inert gas to reduce autooxidation during storage.

lFinished solvent is produced by blending the nonaromatic hydrocarbons from storage zone 41 with the 360-390 aromatic fraction contained in storage zone 22. Blending may be carried out in zone 42 and finished solvent may be withdrawn through line .43. The solvent may contain from about 1 to about 25% of the aro-' matics and from about 75 to about 99% of the nonaromatic fraction. Solvents containing from 4 to 8% aromatics are particularly preferred.

The process of the invention may be further understood by reference to a series of experiments in which solvents of low odor characteristics and high solvent power were produced.

EXAMPLE 1 A naphtha boiling between about 270 F. and about 400" F. was hydrotreated at a temperature of 600 F. :and a pressure of 200 p.s.i.g. with 200 standard cubic feet of hydrogen per barrel in the presence of a cobalt molybdate catalyst. A space velocity of 1.25 volumes of feed per volume of catalyst per hour was employed. The hydrotreated product thus prepared was then contacted with 95 vol. percent of liquefied sulfur dioxide at a temperature of 20 F. The extract phase recovered was treated with a wash oil consisting of 1 Volume of pentane in 2.5 volumes of liquefied sulfur dioxide at 30 F. After vacuum rerunning, a 98% aromatic extract boiling between about 270 and about 400 F. was recovered. This extract was then fractionated in a 15/5 still and vol. percent overhead cuts were caustic Washed and then blended in order to obtain 5 separate boiling range those boiling between about 400 and 500 F. have an extremely disagreeable naphthalene odor.

EXAMPLE 2 Cuts B, C and E from the preceding experiment were blended into samples of an aromatics-free solvent in 15% concentrations. The base solvent consisted entirely of paraifinic hydrocarbons and had a KauriButanol value of 26. The addition of 15% aromatics to this solvent increased the Kauri-Butanol value to about 34. The samples containing 15 aromatics from fractions 13,0 and E in the preceding experiment were tested for odor by a member panel. It was found that the odor of the solvent containing aromatics boiling from about 360 to about 390 F. was appreciably better than that of the sample containing the higher boiling aromatics and that containing the lower boiling aromatics. The results of this test are shown in Table 1H.

Table III SOLVENT POWERS AND ODORS OF BLENDS Blend Kauri-Butauol Avg. Odor Value Score 1 Difference necessary for significance at 90% confidence level is 0.21.

EXAMPLE 3 Cuts B, C and E from Example 1 were also blended into samples of an aromatic-free solvent in 8% concentrations. The base solvent was made by hydrotreating plus hydrogenation as described above, and consistedentirely of naphthenes and parafiins. It had a Kaurifractions. iThese fractions are shown in Table I below. Butanol value of 32. The addition of 8% aromatics to Table 1 INSPECTIONS OF so, EXTRACT CUTS Feed Cut A Cut B Out 0 Cut D Cut E Vol. Percent Distilled 0-30 30-00 60-85 s5-95 95-100 Bolling Range, T... 270-400 270333 333-358 358-390 390-399 399+ Gravity, API 29.0 32.9 30.6 29.0 26.0 23.5 Aromatics, Vol. Percent 98 96 96. 5 96. 5 99+ saturates, V01. Percent 2 4 3. 5 3. 5 2 1 Sulfur, ppm 8 4 5 3 5 I Each of the fractions thus prepared was subjected to -odor panel tests by a 40 member panel and odor ratings on an arbitrary scale were assigned to each fraction. As .shown in Table H, it was found that the aromatic hydro carbons boiling between about 358 and about 390 F. .had a relatively mild odor which was much less offensive :than the odor of the other fractions. iis employed in the improved solvents of the invention. I

It is this out which Table I1 'ODORS OF AROMA'IIC CUTS BY 40 MEMBER PANEL Out Boiling Odor Type Avg. Score 1 Range 2704533 Very Sharp 333-358 Pullgcnt -0. 22

358-390 Relatively Mild +0.23

390-399 Rather Unpleasant... 0. 01

399+ Disagreeable Naphthalene Odor.

Difference necessary for significance at 90% confidence level is 0.24.

It has also been found that aromatics boiling below 270 F. have a very strong benzene-like odor and that this solvent increased the Kauri-Butanol value to about 37. The blended samples were evaluated by a 40 member odor panel. It was again found that the odor of the solvent containing aromatics in the 360390 F. boiling range was significantly better than that of the sample containing the higher boiling aromatics and that containing the lower boiling aromatics.

1 Necessary difierence for significance at confidence level is 0.22.

EXAMPLE 4 Aromatic hydrocarbons boiling between 358 F. and

390 F. were blended into a 300-400 F. boiling point naphtha containing 65% naphthenes and 35% paraffins in concentrations ranging up to about 16% by volume. The samples thus prepared were subjected to odor tests by a member panel. i It was found that the sample containing 4% aromatics had a considerably better odor than either the aromatics-free base naphtha or the samples containing in excess of 8% aromatics. As pointed out heretofore, it is believed that this unexpected discovery can be explained by a masking efiect of the odor of the aromatics upon the odor of the naphthenes.

Although the invention has been described primarily in terms of solvents produced by hydrotreating and subsequently hydrogenating naphthas, it will be understood that the principle of the invention is equally applicable to solvents produced by other well known processes. Solvents of improved solvent powers and odor characteristics can be prepared in accordance with the invention, for example, by blending aromatics boiling between about 360 F. and 390 F. into nonaromatic fractions produced by the polymerization of low boiling olefins such as propylene or by the alkylation of such olefins with low molecular weight paratfins such as butane and isobutane.

What is claimed is:

1. A process for the preparation of hydrocarbon solvents having improved odor characteristics and solvent powers which comprises desulfurizing a petroleum distillate including aromatic constituents boiling between about 360 and 390 F., recovering aromatic hydrocarbons boiling between about 360 and about 390 F. from said distillate, and blending said aromatic hydrocarbons with a substantially nonaromatic, sulfur-free hydrocarbon fraction boiling between about 100 F. and about 500 F. in proportions to produce a blend having an aromatics content of from about 1 to 25% by volume.

2. A process as defined by claim 1 wherein said aromatic hydrocarbons and said substantially nonaromatic fraction are blended in proportions to produce a blend having an aromatics content of from about 4 to about 8% by volume.

3. A process as defined by claim 1 wherein said substantially nonaromatic fraction boils between about 300 and 400 F.

4. A process for the preparation of hydrocarbon solvents having improved odor characteristics and solvent powers which comprises desulfurizing a distillate petroleum fraction boiling in the range between about 100 F. and about 500 F separating said distillate fraction into an aromatic fraction and a substantially nonaromatic fraction, segregating aromatic hydrocarbons boiling between about 360 and about 390 F. from said aromatic fraction, and blending said aromatic hydrocarbons into said substantially nonaromatie fraction in a concentration of from about 1 to about 25% by volume.

5. A process as defined by claim 4 wherein said aromatic hydrocarbons are blended with said substantially nonaromatic fraction in a concentration of from about 4 to about 8% by volume.

6. A process as defined by claim 4 wherein said distillate petroleum fraction is desulfurized by hydrotreating in the presence of a molybdenum-containing hydrotreating catalyst.

7. A process for the preparation of hydrocarbon so1- vents having improved odor characteristics and solvent powers which comprises contacting a petroleum distillate boiling in the range between about F. and about 500 F. with from about 100 to about 2000 s.c.f of hydrogen per barrel under hydrotreating conditions and in the presence of a hydrotreating catalyst, treating said hydrotreated distillate with a solvent selective for aromatic hydrocarbons and recovering an aromatics fraction and a substantially nonaromatic fraction, recovering aromatic hydrocarbons boiling between about 360 and 390 F. from said aromatics fraction, and blending said aromatic hydrocarbons with said substantially nonaromatic fraction in proportions to produce a blend containing from about 1 to about 25% aromatics by volume.

8. A process as defined by claim 7 wherein said distillate is hydrotreated at a temperature of from about 400 to about 800 F. and at a pressure of from about 100 to 1000 p.s.i. in the presence of a molybdenum-containing hydrotreating catalyst.

9. A process as defined by claim 7 wherein said aromatic hydrocarbons and said nonaromatic fraction are blended to produce a solvent containing from about 4 to 8% aromatics by volume.

10. A process for the preparation of hydrocarbon solvents having improved odor characteristics and solvent powers which comprises hydrotreating a straight run petroleum distillate boiling in the range between about 100 F. and about 500 F. in the presence of a molybdenum-containing hydrotreating catalyst; fractionating said hydrotreated distillate and recovering an overhead fraction boiling below about 360 R, an intermediate fraction boiling between about 360 F. and about 390 F. and containing aromatic hydrocarbons, and a bottoms fraction boiling above about 390 F.; hydrogenating said overhead fraction and said bottoms fraction at a temperature of from about 350 to about 600 F. and a pressure of from about 300 to about 1500 p.s.i.g. in the presence of a hydrogenation catalyst; and blending said intermediate fraction with said hydrogenated overhead and bottoms fractions in proportions to produce a blend having an aromatics content of from 1 to 25% by volume.

11. A process as defined by claim 10 wherein said hydrogenation catalyst is a nickel catalyst.

12. A process as defined by claim 10 wherein said intermediate fraction is blended with said hydrogenated overhead and bottoms fractions in proportions to produce a blend containing from about 4 to 8% aromatics.

13. A process as defined by claim 10 wherein said distillate is hydrotreated at a temperature of from about 400 to about 800 F. and at a pressure of from about 100 to about 1000 p.s.i. in the presence of a molybdena-onalumina catalyst.

14. A process as defined by claim 10 wherein said bydrotreating catalyst comprises cobalt molybdate.

References Cited in the file of this patent UNITED STATES PATENTS Haensel Apr. 3, 1956 

1. A PROCESS FOR THE PREPARATION OF HYDROCARON SOLVENTS HAVING IMPROVED ODOR CHARACTERISTICS AND SOLVENT POWERS WHICH COMPRISES DESULFURIZING A PETROLEUM DISTILLATE INCLUDING AROMATIC CONSTITUENTS BOILING BETWEEN ABOUT 360* AND 390*F., RECOVERING AROMATIC HYDROCARBONS BOILING BETWEEN ABOUT 360* AND ABOUT 390* F. FROM SAID DISTILLATE, AND BLENDING SAID AROMATIC HYDROCARBONS WITH A SUBSTANTIALLY NONAROMATIC, SULFUR-FREE HYDROCARBON FRACTION BOILING BETWEEN ABOUT 100*F. AND ABOUT 500*F. IN PROPORTIONS TO PRODUCE A BLEND HAVING AN AROMATICS CONTENT OF FROM ABOUT 1 TO 25% BY VOLUME. 